1. Field of the Invention
This invention relates to graphics controllers and, more particularly, to an automatic monitor sensing graphics controller.
2. Description of the Related Art
With the advent of personal computers, peripheral devices for enhancing the operation and capability of such personal computers are common in the art. One enhancement feature that is sought by many users is color graphics. Since personal computers such as the various types manufactured by IBM first utilized monochromatic display terminals or monitors, color monitors have been adapted for use with these personal computers. Although earlier types of color monitors have acceptable graphics capabilities, their resolution in relation to textual material was poor. Recently, IBM introduced an enhanced color graphics monitor. In order to use the enhanced graphics monitor, an enhanced graphics adapter must be installed in an existing personal computer. The enhanced graphics adapter (EGA) is described in greater detail in IBM Enhanced Graphics Adapter (1984).
As shown in FIG. 1, the EGA, designated 12, is mounted within a personal computer such as the IBM PC, PC/XT or PC/AT. EGA 12, in essence, is a controller that is capable of controlling both color and monochromatic displays. The function and operation of EGA 12 are dependent on the type of monitor that is being used with the personal computer. EGA 12 includes a plurality of signal lines 14, a conventional 8-bit buffer 16, a resistive-capacitive filtering network 18, a 9-pin- connector 20, and a switch 22. If the monitor attached to the computer is an enhanced graphics monitor, the user must place a jumper cable between terminals 1 and 2 of switch 22 so as to permit buffer 16 to transmit signals to pin 2 of connector 20. If the monitor is a monochromatic type or a conventional color type, the jumper will be used to connect terminals 2 and 3 of switch 22 so as to ground line 2. In addition, other switches on EGA 12 must also be used in order to permit it to function with the type of monitor that is attached to the personal computer.
Such manual placement of the jumper and selection of switches are both time consuming and cumbersome. In addition, such manual placement of the jumper and selection of switches increase the possibility of error.